Our co-pending patent application number GB8907788.7 discloses a heat management system for managing the heat generated in an aircrafts' turbofan engine installation. The heat management system described therein comprises basically four major fluid flow sub-systems, namely the engine's fuel system, the engine's oil system, the aircraft electrical power generator's oil system (this generator being driven as an accessory of the engine) and the engine's fan air bleed system. In addition the heat management system comprises a suit of software held for convenience in the memory of the engine's electronic controller, which also has authority over the functioning of the heat management system. For details of the software concepts which, through the electronic controller, control functioning of the heat management system, the reader is referred to the above-mentioned patent application.
The above mentioned fuel system comprises a plurality of fuel flow paths for interconnecting the other elements of the fuel system in a plurality of alternative fuel flow configurations with respect to flow of fuel around the fuel system. Diverting the fuel between the various fuel flow configurations is necessary in order to vary transport of heat around the heat management system and thereby keep various monitored temperatures within preassigned limits.
It is therefore an object of the present invention to provide a fuel control valve arrangement which, when connected to the fuel flow paths in the fuel system, is capable of performing the fuel diversion functions necessary to obtain the plurality of different fuel flow configurations.
Additional flexibility is built into the heat management system by giving it the facility to selectively dump excess heat to the environment either through the fan air bleed system already mentioned, or by returning fuel to the fuel tank in the aircraft's wing after it has been circulated through the fuel system, heat from the fuel being dissipated to the slipstream through the wing.
It is therefore a further object of the present invention to provide a fuel control valve arrangement like the one described above and also capable of selectively allowing return of fuel to the wing tank.
Because dumping heat through the fan air bleed system involves a fuel consumption penalty to the aircraft, it is desirable to utilise this facility as little as possible consistent with maintaining proper control over the monitored temperatures. Consequently, heat dumping by return of fuel to the aircraft wing tank is preferable, where possible, to heat dumping through the other route, and to provide proper control of the amount of heat dumped through the wing, the return flow of fuel to the wing tank should be variable over a range from zero to a maximum.
It is therefore a yet further object of the present invention to provide a fuel control valve arrangement which is capable of combining the required fuel diversion and metering functions.